Mobile display devices such as cellphones and tablet PCs are apt to be damaged when hit or scratched, for example, and thus the users often manually attach a protective film to the surface of their mobile display device on their own. When the users attach a film to a product on their own, they usually attach a film in a typical room environment which is not a controlled environment such as a clean room environment or vacuum. In a typical room environment, however, it is difficult to manually attach a film while sufficiently preventing entry of foreign substances and air bubbles between the product and the film.
One film attachment method that can be manually performed and can prevent entry of foreign substances and air bubbles even in a typical room environment is a method that controls the attachment position of the film and removes air bubbles using soapy water, and then dries the film in the air. This method is used by a professional of film attachment when he or she attaches to a glass window a film on which a company logo or an advertisement is printed. This method has advantages such as a fine control of the attachment position. However, this method is inconvenient for general users because soapy water is required and air-drying takes time, for example. Also, the method can still be improved in terms of preventing entry of foreign substances, though the method can sufficiently remove air bubbles.
Meanwhile, mainly for the case of attaching a film to a product in a factory, there are various known treatment methods and devices for preventing entry of foreign substances and air bubbles between attached surfaces. The common methods here include, for example, a method of performing attachment in a clean room or in vacuum (e.g. Patent Literature 1). For example, for attachment to a liquid crystal panel, a large-scale cleaning system is used.
Patent Literature 2 discloses a method including supplying a liquid whose temperature is higher than the room temperature to eliminate foreign substances and dirt on the surface of the liquid crystal panel. Patent Literature 3 discloses an attachment apparatus configured to automatically clean the surface of the liquid crystal panel body with its foreign-substance-cleaning roller before attachment of a polarizer to the surface.
Other known methods are to remove foreign substances by making the foreign substances stick to an adhesive layer. Patent Literature 4 discloses a foreign-substance-removing adhesive tape whose adhesive layer surface picks up foreign substances on the surface of a product such as a semiconductor wafer and a glass substrate to remove the foreign substances. Patent Literature 5 discloses a foreign-substance-removing sheet designed to be attached to a conveyer member when used, wherein the separator for protection of the surface of the foreign-substance-removing layer is attached to the foreign-substance-removing layer by an adhesive layer.
Also, although it is not designed to prevent foreign substances present in the surrounding air at the time of film attachment from entering between the attached surfaces, Patent Literature 6 discloses a screen protective sheet capable of removing foreign substances stuck to the layer for attachment in the production process by utilizing a removal layer that is obtained by applying and solidifying a liquid resin agent and is to be removed before attachment. This screen protective sheet does not have a function of removing foreign substances on the screen which is considered to be the attachment target.
Similarly, although it is not designed to prevent foreign substances present in the surrounding air at the time of film attachment from entering between the attached surfaces either, Patent Literature 7 discloses a laminated body having a similar structure to the foreign-substance-removing adhesive tape or sheet described in Patent Literature 4 or 5. That is, Patent Literature 7 discloses a long body including a pattern-structure layer, wherein the long object is attached to one surface of a pattern-layer film by an adhesive layer, and a removal film is attached to the other surface of the pattern-layer film by an adhesive layer.